Recommendations for Investigators Using Pigs for Research
by Temple Grandin
DEPARTMENT OF ANIMAL SCIENCE, COLORADO STATE UNIVERSITY,
FORT COLLINS, CO 80523
Pigs are conspicuously sensitive animals who require special attention to guarantee their physical and behavioral well-being in the potentially stress full environment of a research institution.
- Provide pigs with roughage such as oat hulls and straw so that the animals can perform foraging activities and fill their gut. Abnormal behaviors in pigs can be prevented by the provision of straw. Long natural straw is more effective than chopped straw.
Enrich the environment of pigs to counteract frustration and boredom resulting from chronic understimulation. A barren concrete floor offers no stimulation, and it may cause discomfort
and pain resulting from foot and joint irritations and inflammations. Keep the animals on straw
bedding or wood chips to promote foraging and rooting behaviors and to stimulate exploratory behavior. If extreme cleanliness is required provide the pigs with suspended tires and hanging rubber hoses to play with and to chew on. Such objects can easily be sanitized. Cloth
strips are particularly effective enrichment items (Figure 1). Strips of old bedsheet about 3 in.
wide and 24 in. long can be easily tied to the fence and replaced when they get dirty. Environmental enrichment will make the animals calmer and less likely to be startled by sudden noise.
- If experiments last more than a few weeks, avoid using pigs who have been bred for rapid weight gain and
consequently have such a high feeding motivation that supplemental roughage may not satisfy them. Such animals are more susceptible to developing stereotypical behavior and experience impaired well-being if they are kept on a calorie-restricted diet.
- Provide pigs with regular positive human contact in their home pens. Attending care personnel should enter the pens every day and interact with the animals by allowing them to
approach without fear and by stroking them firmly and talking to them gently (Figure 1). This
will produce calmer animals who will be less excited and less stressed during research procedures.
- Allow the pigs to run up and down the aisle at least once a week. This gives the animals
some extra exercise and reduces their fear when they have to be moved from their pen to
- When a pig has to be removed from the home pen for a research procedure, always take
another familiar pig along. Pigs are social animals who quickly become apprehensive, agitated and distressed when they are separated from their herdmates.
- Do not subject pigs to forced movement and handling procedures. Pigs are intelligent
animals andwith a good understanding of their species-typical behavior and sensory physiologycan be readily trained to cooperate during common research procedures. When training pigs to work with rather than against you, never punish them but reward them with highly palatable treats. The training does take a little extra time, but researchers who have used
trained pigs in their laboratories find that the benefits are worth the time investment. Trained
animals experience less stress and hence provide more reliable research data. Needless to say,
a well-designed training program also serves as a mental stimulation not only for the pigs but
also for the care personnel.
- House pigs in compatible groups to account for their strong social disposition. Avoid
disrupting the composition of the group; this will help the animals to form stable social relationships and avoid aggressive conflicts.
- If the research protocol requires temporary single-housing, allow the animal to keep visual
contact with other familiar pigs. If this is not possible, provide the pig extra physical contact
with a friendly familiar person. Patting a pig is not a waste of time because it improves scientific methodology by making the animal feel more at ease in a potentially distressing situation.
- Do not tether pigs. Being tethered is a chronic stress situation for them.
- Pigs are motivated to move for the sake of movement. It is therefore an imperative to
provide single-housed animals enough room not only to lie fully relaxed without head or nose
touching the feeder but also to turn around freely.
Suggested Further Reading
Arnone M and Dantzer P 1980, Does frustration induce aggression in pigs? Applied Animal Ethology 6, 351-362.
Beattie, VE, Walker N, and Sneddon IA 1995. Effects of environmental enrichment on
behaviour and productivity of growing pigs. Animal Welfare 4, 207-220.
Fraser D 1975. The effect of straw on the behavior of sows in tether stalls. Animal Production 21, 59-68.
Grandin T 1989. Effect of rearing environment and environmental enrichment on behavior
and neural development in young pigs. Doctoral dissertation, University of Illinois, Urbana.
Grandin T 1986. Minimizing stress in pig handling. Lab Animal 15(3), 15-20.
Helmsworth PH, Barnett JL and Hansen C 1981. The influence of handling by humans on
the behavior, growth, and corticosteroids in the juvenile female pig. Hormones and Behavior
Janssens CJJG, Helmond FA and Wiegant VM 1994. Increased cortisol response to exogenous adrenocorticotrophic hormone in chronically stressed pigs: Influence of housing conditions. Journal of Animal Science 72, 1771-1777.
Lawrence AB and Rushen J 1993. Stereotypic Animal Behavior: Fundamentals and Applications for Animal Welfare. CAB International: Wallingford
McFarlane JM, Curtis SE and Widowski TM 1988. Turning and walking by gilts in modified
gestation crates. Journal of Animal Science 66: 326-333.
Stolba and Wood-Gush DGM 1980. Arousal and exploration in growing pigs in different
environments. Applied Animal Ethology 6, 382-383.